What if i turned that around, and said: Until Marciano shows me he is able to handle a world class, 6'6 245lbs skillful boxer with fast hands and top end power and beat him handily..... there is no way I can ever realistically pick him over Wlad.

Difference is his while Marciano is unproven against this type of fighter...Wlad already proved in the brewster purrity and even peter fight he is highly incapable against vastly inferior relentless punchers in the mold of a marciano. While Marciano is unproven...Wlad has technically proven a failure.